لخّصلي

FROM SPECIES TO ECOSYSTEM
Photosynthesis is the base of all ecosystem.
Ecosystem is a dynamic and complex system of plant, animal, and microorganism communities and their environment, all interacting as functioned unit with defined physical location.

Species: refers to all organisms of the same kind that are genetically similar.
A population consists of all members of species living in a given area at the same time.
An ecological system, or ecosystem, is composed of a biological community and it is physical environment.
Biomass is total amount or weight of living organism.
Secondary productivity
Example of food chains:
A linked feeding series, now think about a more complex food chain involving you. (A chicken – a corn plant, and a grasshopper).
The chicken could eat grasshopper that had eaten leaves of the corn plant, you (as human) also could eat the grasshopper directly, some humans do.
Think about what you have eaten today and trace effect it back to its photosynthetic source if you have eaten egg you can trace it back to a chicken, which ate corn.
Egg- Chicken – Conn

	Human                   Grasshopper 

Organism that photosynthesize – plants, algae known as producers
Photosynthesis is described as primary productivity.
Manufacture biomass by organism that eat plant is called secondary productivity, for e.g. of food chain
Food chain: the process of transfer energy from one organism to another.
Food web: is interconnected of food chain.
The Trophic level: A hierarchical series of organisms each dependent on the next as assurance.
The step of flowing energy on an ecosystem.

Producers: They are organisms which are capable of producing food from simple substances.
Consumers: they are organisms which are incapable of producing their food, and they consume other organism.
Consumers comprises of:
1- The herbivores: feed on plants (plant eaters)
2-The carnivores: feed on meet or flesh.
3- The omnivores: feed on both plant and animal.
4-The scavengers: feed on remains of predators.
Decomposers: They are organism that breaking down or decaying dead organic or inorganic materials.

Material Cycles and life processes
The earth is plant that provide life in our solar system because its environment. Require constant cycling of material between biotic and a biotic component of ecosystems.
1.The hydrological cycle.
2.Carbon cycle.
3.Phosphorus cycle.
4.Nitrogen cycle.
5.Sulfur cycle.

(1)The hydrological cycle.

The path of water thorough our environment known as hydrogen cycle.
Most of the earth’s water is stored in oceans, but solar energy evaporates this water, and winds distribute the water vapor around the globe (Earth).
Living organisms emit the moisture, they have consumed through respiration, and perspiration.
Atmosphere enters lakes and streams and return to the ocean again.

(2)Carbon cycle.

Carbon is a part of rock, living things and air, which is present in the atmosphere in small amount. The carbon atom collect in the atmosphere with oxygen in the form of carbon dioxide and carbon monoxide.
Carbon moves from the atmosphere to plants by collecting it through the process of photosynthesis and transfer to the animals (herbivores) in form of energy or food, and when animals or plants die the carbon move to the soil.
Also the plants and animals add carbons to the atmosphere through the respiration, and human by burning of fossil fuels and the factories adding more carbons to the atmosphere.

(3)Phosphorus cycle:

The source of phosphorus is the rocks, and it’s soluble in water as phosphate.
Phosphorus compounds are removed from rocks by weathering and erosion and carried by rains to soil and water, then plant absorb phosphorus from soil by the roots and transfer to the animals when they eat the plants.
Phosphorus released to soil again from living through excretion of urine and when they die.

(4)Nitrogen cycle

Nitrogen is an important element because cannot exist without amino acids, and proteins, all of which are organic molecules containing nitrogen. The nitrogen atoms that form these important molecules are provided by producer organisms. Plants take up inorganic nitrogen from the environment and used it to build their own protein molecules, which are eaten by consumers' organisms, digested, and used to build up their bodies.
Even though nitrogen is the most abundant gas (about 78% of the atmosphere), however plants cannot use N2 molecule in the air.

The key natural processes that make nitrogen available are carried out by nitrogen fixing bacteria (including some blue-green algae) these organisms have highly specialized ability to fix nitrogen, meaning they change it to less mobile, more useful forms by combining it with hydrogen to make ammonia (NH3).

Nitrite-forming bacteria combine ammonia with oxygen, forming nitrites, which have the ionic form NO2. Another group of bacteria then convert nitrites to nitrates, which have the ionic form NO3 that can be absorbed and used by green plants. After nitrates have been absorbed into plant cells they are reduced to ammonium NH4+, which is used to build amino acids that become the building blocks for proteins.
Nitrogen reenters the environment in several ways. The most obvious path is through the death of organisms. Their bodies are decomposed by fungi and bacteria, resulting ammonia and ammonia ions which then are available for nitrates formation.
How does nitrogen reenter the atmosphere, completing the cycle?
Denitrifying bacteria break down nitrates into N2 and nitrous oxide (N2O) gases that return to the atmosphere, thus denitrifying bacteria compete with plant roots for available nitrates.
(5) Sulfur cycle:
Sulfur plays a vital role in organisms, especially as a minor but essential component of protein. Sulfur compounds are important determinants of the acidity of rainfall, surface water, and soil. In addition, sulfur in particles and tiny air-borne droplets may act as critical regulators of global climate. Most of the earth sulfur is tied up in rocks and minerals such as iron disulfide or calcium sulfate. This inorganic sulfur is released into air and water by volcanic eruptions.
Inorganic processes (volcanic eruptions) is responsible for the release of sulfur to the environment. Also living organisms, especially bacteria sequester sulfur in biogenic deposits or release it into the environment.
Human activities also release large quantities of sulfur through burning of fuels. Sulfur dioxide and sulfate causes human health problems, damage buildings and vegetation, and reduce the visibility. They also absorb UV radiation and create cloud cover that cools cities.